摘要
湖泊沉积物元素地球化学是探讨湖泊沉积环境的有效代用指标之一。通过青藏高原北缘柴达木盆地湖相沉积剖面沉积物中酸溶组分(AS)和酸不溶组分(AI)常量元素(K,Ca,Na,Mg,Ti,Fe,Mn和Al)的测试,分析了不同组分中常量元素的分布特征及其元素含量与矿物组成的关系。结果显示:剖面中常量元素的组成与沉积物矿物成分密切相关,酸溶组分与酸不溶组分中元素含量差别较大,揭示出不同组分对湖泊沉积环境的响应模式存在差异。其中,沉积物酸不溶组分中的Al、Fe等元素与石英矿物相对含量变化呈负相关,而与粘土矿物相对含量呈正相关,揭示出酸不溶组分元素变化与湖泊流域物质组成或风化强度等信息有关。沉积物酸溶组分常量元素含量相对较低,Na和Ca等活泼元素在酸溶组分中相对富集,与碳酸盐含量有较好的相关性,主要形成于湖泊自生作用。通过与常规代用指标沉积物粒度和87Sr/86Sr对比分析,贝壳堤剖面酸溶组分Mg/Ca比值部分继承了源区的信号,不能直接响应于湖泊盐度的变化。利用去趋势方法,去趋势后酸溶组分Mg/Ca比值与中值粒径及锶同位素比值呈现较好的正相关性,响应于传统的盐度模式解释,揭示了Mg/Ca比值指示湖泊环境变化的可靠性,综合分析不同组分的地球化学元素信息在提取和解译沉积物元素地球化学的环境代用指标方面具有重要意义。
The chemical elements of lacustrine sediments were sensitive to climatic change. Based on the measure- ment of major elements （K, Ca, Na, Mg, Ti, Fe, Mn and A1） of acid soluble （AS） and acid insoluble （AI） fractions of the Shell Bar Section from Qaidam Basin in NE Tibetan Plateau, the correlations of major elements with mineral assemblages,grain-size,content of carbonate and STSrTS6Sr value were discussed. There was a strong correlation be- tween major elements and minerals. Element Concentration of AS fraction shows larger various than AI fraction,in- dicating different response with environment change to AI and AS fractions. Elements A1 and Fe concentration of AI fraction have a negative correlation with quartz and a positive correlation with clay mineral, indicating the weathering information in basin was recorded by AI fraction. The total concentration of AS fraction was lower and had a strong correlation with carbonate concentration, indicating the AS fraction was authigene in lake system. The correlations of Mg/Ca ratio in AS fraction with grain-size andSTSr/S6Sr were analyzed, Mg/Ca in AS was influenced by Mg/Ca val- ue of bedrock and failed to be used as index of salinity. Using detrending method, Mg/Ca in AS by recalculated showed strong correlation with grain-size and STSrfS6Sr . So Mg/Ca was a reliable index of salinity in lake system. The chemical element analysis of AS and AI fractions was useful to extract and understand the climate signal recor- ded by lake sediment.
出处
《山地学报》
CSCD
北大核心
2013年第2期174-183,共10页
Mountain Research
基金
国家自然科学基金项目(41101189)
福建省公益类科研院所专项基金项目(2011R1037-7)~~
